The nephew of a man arrested in error by police in Blenheim at the weekend has been an illegal overstayer for 10 years and used his uncle's identity to avoid being deported, police say.

They have issued an arrest warrant for Siale Afuhia Fuapau and are asking his family and other people in the region to help find him.

Immigration New Zealand also have a deportation order for the 31-year-old Tongan man.

Police believe Siale Fuapau was the man who gave them the details of his uncle, Vaiola Fuapau, when he was arrested in September and charged with entering a building with intent to commit a crime and resisting police.

The false details led to his uncle being arrested and locked in the Blenheim police cells for two nights at the weekend.

Tasman police district commander Superintendent Richard Chambers said yesterday a police investigation this week had revealed Siale Fuapau had been an illegal overstayer in New Zealand since 2002 and had used his uncle's name "for some time" with government agencies to avoid being deported.

Police were confident people close to him knew where he was and knew about his immigration status. "I believe they have been in close contact with him during the time he has been in Marlborough. I believe those people have information that would assist us with our inquiries and remind them that it is an offence under the Immigration Act to aid and abet a person to remain in New Zealand."

However, Vaiola Fuapau said last night he had not seen his nephew for about three weeks and he did not know where he was.

Mr Chambers said since Vaiola Fuapau had provided police with his nephew's name, they had withdrawn the charges against him and laid them against his nephew.

Tasman police communications manager Barbara Dunn said that, along with the two charges he already faced, Siale Fuapau was likely to face other charges.